Setting up speakers with sound level meter

[admin_exported]

I was about to watch the guide of how to do this but cant get on there at the minute and as im desperate to get it sorted thought id ask a quick question! I vaguely remember from watching it ages ago you set the time to slow and then set each level to 67.5 is this correct? Thanks

 

[Anonymous]

No its 75 answering my own questions now!

 

[professorhat]

Set mine up recently and used Mr E's advice of using the slow setting and used 75dB as my baseline. Said thread can be found here.

 

[Anonymous]

Thanks.

 

[Anonymous]

just out of curiosity professorhat how close did you get your sub to 75db i got to around 65 and i couldnt go any louder as it was just too much at that point!

 

[professorhat]

Wasn't a problem for mine I have to say. Mind you, since I have a wooden floor and live in a ground floor flat, my sub is sitting on one of these which might help.

 

[professorhat]

flairdj:just out of curiosity professorhat how close did you get your sub to 75db i got to around 65 and i couldnt go any louder as it was just too much at that point!ÿ

Had a similar issue with my B&W ASW610 that I've just got - switched the sound meter to use C weighting as opposed to A (as directed in the B&W manual) and this was then fine.ÿ

ÿ

 

[Tom Moreno]

Technically, your rears should be set at 72db. When we calibrate our mixing stages the specification for 5.1 systems is that the rear channels produce a total of 85db (85 is the cinema reference) and as volume is doubled/halved when you go up or down 3db, you set each of the surround channels to 82db and when the tone comes out of both together it will be 85, same as each of your front three channels. This is a common misconception when people set up home systems and often the rears are 3db too hot. If you play a THX trailer that has the man flying around the room you should hear that the volume level doesn't fluctuate as he goes 'round the back when your rears are set at 72db, but if you set everything to 75 the swing round the back of the room will be slightly exaggerated.

Some people have grown accustomed to and/or prefer the extra wow-zing factor of having the rears a bit too hot and many manufacturer's manuals instruct you to do it as well, but if you really want to hear the film as it was mixed on the soundstage...

 

[professorhat]

Interesting - thanks for this Tom, I'll have a play when I've got a few minutes.

 

[Big Chris]

Did it make much difference to the auto set-up Prof?

And the other big question is: Who's gonna come round and do mine for me?

;-)

 

[Hems]

For some reason on my 2400es I couldnt reach 75dB with Sound Level Meter. However I just found out that you can change the volume when the test tone is running, which explains the earlier problem. Now should the volume be set at 0db when running the test tone so that I can take measurements?

 

[aliEnRIK]

Hems:For some reason on my 2400es I couldnt reach 75dB with Sound Level Meter. However I just found out that you can change the volume when the test tone is running, which explains the earlier problem. Now should the volume be set at 0db when running the test tone so that I can take measurements?

Yes you should

 

[aliEnRIK]

Can anyone explain to me why setting should be to 75 DB and not another figure (Say 80)?

 

[Tom Moreno]

It was never set in stone that reference level for home theatre would be 75db, it was assumed and eventually became the defacto standard. The reference level for all cinemas is 85db. This number was arrived at due to it's relationship that 85db is the loudest level our ears can sustain constantly over a two-hour period without producing hearing loss (and why union rules on mixing stages demand that mixers have a 15 minute break every 2 hours to reset their ears). Due to the fact that cinemas are generally larger rooms then you living room and often filled with more people that dampen the sound (or the film needs to be heard over), and also that people often spend longer than two hours listening to their home systems, it was generally regarded at the beginning of this whole home theatre craze that we should set our reference levels a bit lower for home. That said, there were quite a few people who set their systems up using 85db as their reference 10-15 years ago. Some time around the introduction of DVD the idea of using 75db as the home reference gained a bit of traction and eventually stuck. I'm not certain where 75 came from as a number, most likely as it is a nice round 10 db less than the cinema ref (although relationships of 10s are really insignificant in decibels, it's an exponential scale that moves on the basis that a change of 3db is perceived as a doubling or a halving of perceived volume).

 

[aliEnRIK]

Good answer Tom!

I asked as I set mine generally a bit higher and wondered if I was doing wrong by doing so (clearly not)

 

[pwiles1968]

Following on From Tom's great Post, while 3dB is a real Doubling of volume or Power, the Human Ear is not linear and it requires 10dB of change for a Person to perceive a doubling or halving in sound level, I'm not familiar with cinema setups but it is possible they chose 10dB for that reason.

 

[professorhat]

Big Chris:Did it make much difference to the auto set-up Prof?And the other big question is: Who's gonna come round and do mine for me?;-)

Definitely sounded better once adjusted from the Auto levels (which were quite a way off the sound meter levels in some cases). Haven't yet tried the 72dB on the rears yet (been a busy weekend).